\documentclass[12pt]{article}
 \textheight15cm \textwidth11cm \parindent0mm \parskip 1ex plus2ex minus0.8ex
\begin{document}
A \verb|\input| command is very useful. 
\verb# 1   2 3# and \verb*# 1   2 3#.

\begin{verbatim}
C     Fortran program which computes the area of a circle
      real pi,r,f
      pi=3.14159265
      write(*,'(1x,a,$)') 'Please type in radius: '
      read(*,*) r
      f= r**2 * pi
      write(*,*) 'The area of a circle with a radius ',r,' is ',f
      stop
      end
\end{verbatim}
 
\begin{verbatim*}
ls -l *.tex *.aux
rm -i *.aux
\end{verbatim*}
\end{document}
